Automatic start-up devices for a steamelectric generating plant



March 9, 1965 c. STROHMEYER, JR 3,172,266

AUTOMATIC START-UP DEVICES FOR A STEAM-ELECTRIC GENERATING PLANT FiledFeb. 26, 1963 2 Sheets-Sheet 1 STEAM GENERATOR 5 coususnou 9 i CONTROLWATER m STEAM our SYSTEM WATER LEVEL l3 I4 1. .2 l 3 REGENERATIVE FIXEDOR RATE OFMETAL FEEDWATER 5E5??? EEQIG RQELER cm: CONTROLLER F lg. 3.

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I04u 78 o A 73 INVENTOR. CHARLES STROHMEYER ,JR.

IS ATTORNE March 9, 1965 c, STROHMEYER, JR 3,172,266

AUTOMATIC START-UP DEVICES FOR A STEAM-ELECTRIC GENERATING PLANT FiledFeb. 26, 1963 2 h hee 2 Fig. 2. INVENTOR CHARLES STROHMEYER,JR.

EXAM 66M his ATTORNEY United States Patent 3,172,266 AUTOIVIATICSTART-UP DEVICES FOR A STEAM- ELECTRIC GENERATING PLANT CharlesStrohrneyer, In, Wyomissing, ia, assignor to Gilbert Associates, Inc,Reading, Ya. Filed Feb. 26, 1963, Ser. No. 261,177 4 Claims. (Cl.50-105) This invention is a continuation-in-part of patent applicationSerial No. 42,194, filed lune 7, 1960; Serial No. 81,187, filed January6, 1961; and Serial No. 154,087, filed September 5, 1961, now abandoned.

This invention relates to devices and systems for improving theoperating flexibility of steam-electric generating units including steamgenerator, turbine generator and auxiliary equipment.

An object of the invention is to provide a novel apparatus and a systemwhich will reduce unit start-up time and costs, as well as provide thesteam generator with capability to vary primary outlet steam temperatureto control the rate of metal temperature rise within the turbine duringstartup.

A more specific object of the invention is to provide a simplifiedautomatic control system for the steam generator during startup wherebythe conventional automatic combustion control system is fed a fixed orprogrammed loading signal from the startup control system which islimited by a rate of metal temperature rise with respect to the strengthor gain of the signal.

A further specific object of this invention is to provide a means forusing the above mentioned control system with a steam generator having athrottling valve means located intermediately in the steam generatorfluid circuits between the water inlet and superheated steam outlet, aflash tank, a flow controlled bypass conduit from an intermediate partof the steam generator through fluid circuit upstream of said throttlingvalve means which discharges to said flash tank after pressure reductionthrough said flow control means, conduit and flow control meansconnecting the separated steam spare of said flash tank with the steamgenerator intermediate fluid circuits downstream of said throttlingvalve means, a regenerative feedwater makeup cycle and a heat sump,means to selectively flow flash tank separated steam to said steamgenerator downstream circuits, regenerative feedwater makeup cycle andto said heat sump, and means to selectively flow flash tank separatedliquid to said regenerative feedwater cycle and to said heat sump.

Other objects and advantages of the invention will become more apparentfrom a study of the following description taken with the accompanyingdrawings wherein:

FIG. 1 is a diagrammatic or schematic showing of a startup combustioncontrol loading system wherein a fixed or programmed loading signal tothe steam generator automatic combustion control system is over-riddenby measurement of rate of metal temperature rise in the steam generatoror connected turbine driver;

FIG. 2 is a detailed application of the FIG. 1 control system;

FIG. 3 is a schematic showing of a steam generator startup fluid flowcontrol system as described above in the further specific object of thisinvention; and

FIG. 4 is a schematic showing of the integrated steamelectric generatingplant arrangement, including the startup combustion control loadingsystem and the steam generator fluid control system.

General description of present invention In the specification below, thefollowing control action descriptions apply:

Proportional control action.Position of final control element islinearly proportional to value of controlled variable;

Reset (integral) control action-Rate of motion of final control elementis-linearly proportional to deviation of controlled variable fromnormal;

Rate (derivative) control action.Position of final control element islinearly proportional to rate of change of controlled variable.

FIG. 1 shows a startup combustion control loading system for a steamgenerator wherein a fixed or programmed loading signal to the steamgenerator automatic combustion control system for controlling firingrate, including fuel and air flow, is over-ridden by measurement of rateof metal temperature rise. The startup control system for the steamgenerator may consist of manually adjustable controller 1 which sends afixed or programmed variable loading signal to the steam generatorautomatic combustion control system 4. Measurement of rate of metaltemperature rise in controller 3 varies the signal from controller 3 tosumming relay 2 which may decrease or increase, or alternately increaseor decrease the loading signal from controller 1 on its way tocombustion control system 4 to increase or decrease the steam generatorfiring rate so as to control steam generator outlet steam temperature ina way which will hold the rate of metal temperature rise within limitvalues established by settings in the rate of temperature risecontroller 3. Rate of metal temperature rise may be measured at anycritical steam generator part, as the superheater steam outlet header orany critical part of a turbine receiving steam from the steam generator,as the steam admission parts or turbine inner cylinder.

The above described system can be constructed from standard pneumatic orelectric control components available from manufacturers of steamgenerator automatic combustion control systems.

FIG. 2 is a practical detailed application of the FIG. 1 startupcombustion control loading system. The box control systems 1, 2, 3 and 4are shown by dot-dash lines. During startup when warming up the steamgenerator from a cold state, the superheater outlet steam header metaltemperature causes thermocouple 46 embedded in the metal to generate anelectrical voltage potential in thermocouple leads 47 and 47a whichterminate in cold reference junctions 48 and 48a. The cold referencejunc tions are connected through circuits 49 and 49a to a direct currentreceiver 50 as manufactured by the Bailey Meter Co., Class E3 shown inpage 7 of their product specification E12-5, copyright by Bailey MeterCo., 1958, Form No. CEl2-5E printed June 1961. A 0 to 50 volt directcurrent output signal from the receiver 50 retransmitting slidewire issent through circuit 51 to direct current operational amplifier rateaction unit 52, as manufactured by the Bailey Meter Co., Part No.66l13001 as shown on page 3 of their product specification E933,copyright by Bailey Meter Co. 1960, Form No. CE93-3 printed January1960. The 0 to 5 volt direct current output from rate action unit 52 istransmitted through circuit 53 to direct current operational amplifierproportional action unit 54 as manufactured by the Bailey Meter Co.,Part No. 6611297-1 as shown on page 3 of their product specificationE933 referenced above. The O to 20 volt direct current output signalfrom action unit 54 is transmitted through circuit 55 to direct currentreceiver 56 as manufactured by the Bailey Meter Co., Class E7 as shownon page 7 of their product specification E12-5 referenced above.

Receiver 56 output is in the form of mechanical positioning throughrotating lever arm 56a which is connected to a similar lever arm 58athrough linkage 57. Lever arm 56a drives lever arm 58a a relativeamount. Lever arm Patented Mar. 9, 1965 a 58a acts on the pneumatictransmitter 58 so as to regulate the control air pressure in conduit 59.Transmitter 58 is as manufactured by the Bailey Meter Co., Class P asshown on page of their product specification E12-5 referenced above.

Thus, the control air pressure in conduit 59 is a function of metaltemperature change in superheater outlet steam header 45. As the rate ofmetal temperature rise increases, the pressure in conduit 59 willdecrease to a minimum of 3 p.s.i.g. As the temperature in header 45stabilizes so that there is no change, pressure in conduit 59 increasesto a maximum of 27 p.s.i.g. The conduit 59 feeds through check valve 60to conduit 59a. Conduit 61 bypasses check valve 60 and contains a needlevalve 62 for throttling purposes. Flow through valve 62 is smallcompared with How through valve 69. Flow in conduit 61 is twodirectional.

Conduit 59a feeds to volume chamber 63 which is provided with a ventconduit 64 exhausting to atmosphere. Conduit 64 contains a needle valve65 to permit only very small leakoif flows through the vent line 64. Theneedle valves 62 and 65 in conjunction with check valve 60 pre ventrapid pressure decay in volume chamber 63 as a result of sudden pressuredrops in conduit 59. The volume chamber also slows up pressure increaseas a result of momentary pressure rise surges in conduit 59. In effectthis arrangement stabilizes and averages air pressure for short periodsof time in the volume chamber 63. The downstream conduit 66 connects toproportional plus reset computing relay 67 as manufactured by the BaileyMeter Company and as shown in FIG. 10 on page 4 of their productspecification P99-3, copyright by Bailey Meter Co., 1956, Form No.CP99-3D, printed Mach 1960. Conduit 66 connects to the B chamber ofrelay 67. The A chamber is vented and the C and C1 connections areplugged. The A-B beam (not shown) is spring loaded to increase thecontrol air output pressure from chamber D to conduit 63 as the pressurein chamber B through conduit 66 decreases below the balance loading ofthe spring, the output pressure from chamber D will integrate down to 3p.s.i.g. minimum.

The A-B beam spring loading corresponds to the limit allowed for rate ofmetal temperature rise in superheater outlet steam header 45 beforecontrol action to steam generator firing rate is initiated from systemcontroller 3. From operatin experience and observation of actualmeasured rate of temperature rise, the spring can be calibrated tocontrol the process so that firing rate adjustment at system controller1 will not cause the rate of metal temperature rise to exceed say 500degrees F. per hour.

The block control system 4 is a segment of the overall combustioncontrol system for the steam generator. Only those features used forcontrol of fuel and air flow for startup are shown in elemental form asthe specific form of the fuel and air feed mechanisms are not a part ofthis invention. Fuel oil firing is shown for illustrative purposes.

Control box 1 sends a signal to control box 4 through conduits 73 and 78which automatically controls the rate of fuel and air feed to steamgenerator furnace 95. As long as rate of metal temperature rise inheader 45 does not exceed the limit of relay 67, there will be noadjustment to the control signal between 1 and 4 from temperaturemeasurement. As rate of metal temperature rise in header 45 exceeds thelimit in relay 67, control box 2, or relay 69 will reduce the strengthof the control signal from control box 1 and reduce firing rate incontrol box 4 until the limit of relay 67 is restored.

Metal temperatures in thick walled structures for high pressure steamgenerators do not change rapidly in the superheat zones. Therefore, byapplying corrective control action'before the physical maximum limit isreached, allows time for correction before damage occurs. The controllimit in relay 67 should be set below the actual maximum physicalallowable limit in header 45.

Control box 1 contains a manual loader 70 which has a control knob 70awhich regulates the output air pressure in conduit 71 from 3 to 27p.s.i.g. Air pressure is registered on scale 7%. Manual loader 70 ismanufactured by the Bailey Meter Co., Type AS2300 and as shown in FIG. 6on page 3 of product specification P992, copyright by Bailey MeterCompany 1957, Form No. CP99-2B printed July 1960. Increases in airpressure from loader 70 increase firing rate in control box 4. Conduit71 connects to remote adjustable computing relay 72 as manufactured bythe Bailey Meter Co., Type No. AR8031A and as shown in FIGURE 4 on page2 of product specification P99-9, copyright by Bailey Meter Company1957, Form No. CP999A, printed August 1960. The control signal in theform of air pressure may pass through relay 72 proportionally withoutalteration of the proportional setting or the proportional setting maybe programmed to change with time.

Program controller 75 as manufactured by the Bailey Meter Co., Class Tand as shown on page 9 of their product specification E12-5 referencedabove, is provided with a cam which can be shaped to rotate lever arm75a with time. The speed of rotation of the cam can be lengthened byinterrupting the power supply to the controller 75 drive unit at presetintervals using known power supply interrupting devices therebyadjusting the time constant suitable for various conditions of the steamgenerator from cold to hot startup.

Controller 75 through lever arm 75a and connecting link 76 to lever arm77a controls the output air pressure from pneumatic transmitter 77 whichis identical to item 58 above. The output air passes through conduit 74to chamber L in relay 72 adjusting the proportion band setting andchanging the output air pressure in conduit 73 with respect to the inputair pressure in conduit 71. Thus, for any given loading signal inconduit 71 from loader 70, the output signal from relay 72 can beprogrammed to increase with time. As a substitute for items 77 and 75,air pressure variations in conduit 74 can be controlled proportionate tosteam flow variations to a steam consumer connected to the superheateroutlet of the steam generator.

The output from relay 72 feeds through conduit 73 to proportionalcomputing relay 69 as manufactured by the Bailey Meter Co. and as shownin FIG. 8 on page 4 of their product specification P99-3 referencedabove. Conduit 73 feeds to item 69 chamber A and conduit 68 feeds toitem 69 chamber B and thus item 69 performs the function of subtractingthe conduit 68 significant air loading pressure from the conduit 73significant air loading pressure. Item 69 can be considered as a summingrelay where the increasing pressure in conduit 68 is functionallyreverse to the increasing pressure in conduit 73.

The 3 to 27 p.s.i.g. air output signal from item 69 chamber D to conduit'78 feeds to combustion control system 4 and to three-way valve 79 whichtransfers master control of fuel and air flow to controllers 1, 2 and 3during startup. During normal operation, the control of fuel oil flowwould be initiated through control air conduit 81 with the valve 79rotated 90 degrees counter clockwise as shown. Valve 79 discharges toconduit which connects to positioning relay 82 as manufactured by theBaileyMeter Company and as shown in their product specification P99-5,copyright by Bailey Meter Co. 1957, Form No. CP995A, printed April 1960.Relay 82 feeds power air through conduit 33 to diaphragm air poweroperator 84 which opens or closes the fuel oil supply valve 85. Relay S2is provided with a cam and mechanical position indicating linkage 105 tothe valve 85 operator so that valve opening can be compensated in a waywhich will linearize flow quantity through the valve with respect tochanges in conduit 80 control air pressure to the relay 82. Fuel oilflow will be approximately proportional to control air pressure inconduit 80. Thus, control boxes 1, 2 and 3 regulate fuel feed to thesteam generator.

The same control signal to valve positioner 82 may also be supplied in asimilar fashion to the furnace combustion air flow controls, not shown,or air flow maybe controlled as shown in box 4. Fuel flow through valve85 and conduit 86 passes through flow measuring orifice 87. Conduits 88and 89 on both sides of the orifice conduct fuel oil pressure to flowmeter and transmitter 90. Flow measurement in the form of air pressureis transmitted from 90 through conduit 91 to proportioning and resetcomputing relay 92 as manufactured by the Bailey Meter Company and asshown in FIG. 10 on page 4 of their product specification P99-3referenced above. Combustion air is fed through conduit 97 to burnerwindbox 96 which distributes air to fuel oil burner 100 through damperregisters 102. Pressure drop from the windbox to the furnace is afunction of flow. Pressure differential measurement is made by sensingand computing means 94 from the windbox 96 to the furnace 95 throughpressure conduits 98 and 99 respectively. Fuel flow measurement signalvs. air flow measurement signal through conduits 91 and 93 are adjustedso that air flow is truly compared with fuel flow in relay 92 and thecontrol air output signal through conduit 103 impulses the combustionair supply controller 104 to maintain the preset fuel-air ratioestablished in relay 92 by adjustment of damper 104a in air supplyconduit 97. Such type of air flow control has been in standard use formany years.

In FIG. 2 electric power and air supplies to the various controllershave not been shown and are covered in the referenced productspecifications. FIG. 2 shows the electric and pneumatic control circuitsand their interrelation one with the others.

16. 3 shows a steam generator startup fluid flow control system whichmay be used in conjunction with the combustion control loading systemshown in FIG. 1. In the flow control system of FIG. 3, the steamgenerator 5 has a throttling valve means 9 located intermediately in themain fluid flow circuit between the water inlet and main steam outlet. Abypass conduit from an intermediate location in the main flow circuitupstream of valve means 9 discharges to flash tank 6 after pressurereduction throughthrottling valve means 7. Steam from flash tank 6 maybe returned through conduit and valve flow control means 8 to the'steamgenerator main flow circuit at some intermediate point downstream ofvalve means 9.

The flash tank is normally operated during startup at an intermediatepressure whose saturation temperature is substantially above thedesigned operating limit of any associated heat sump as heat sump andwhich intermediate pressure is substantially below that in the steamgenerator fluid circuits upstream of valve means 9, especially whenfirst opening valve means 9.

When the valve means 8 is open, valve means or is throttling to apressure not in excess of the flash tank 6 design pressure. For higherdownstream pressures in the main flow circuit, valve means 8 is closedor flow from the main circuit downstream of system 9 to the flash tankis prevented by means of a check valve or other reverse flow preventerin conjunction with or as a substitute for valve means 8.

When the startup combustion control loading system of FIG. 1 is used fora steam generator having a fluid flow control system shown in FIG. 3,increasing firing rate will increase the enthalpy of the steam generatoroutlet steam as will as the amount of heat in the fluid discharging tothe flash tank. Surplus flash tank heat may be discharged to a heat sump10 as a condenser in the form of steam through flow control valve 12, oras liquid drains through flow control valve 14. Flash tank heat may beused in the regenerative feedwater cycle as steam through flow controlvalve 15, or as liquid drains through flow control valve 13. When thefiring rate is in balance with the steam generator outlet steam flow 9is shut and. the regenerative feedwater cycle flow requirements from theflash tank, there will be no flow through control valves 12 and 14.Increasing the firing rate above the balanced condition is the meansused for raising outlet steam temperature and superheater metaltemperatures. Heat may be extracted from the drain flow from flash tank6 before it is discharged to heat sump 10 through control valve 14 bymeans of a heat exchanger in the feedwater cycle (not shown) so that forany given heat input to the flash tank through flow control valve 7, theamount of drains to the heat sump 10 may be increased. Flow of fluidfrom the flash tank to the heat sump 1i) permits cooling of the fluid sothat it may be passed through low temperature water purificationequipment as a liquid before return to the steam generator circuits.

Pressure in the steam generator main flow circuit downstream of valvemeans 9 may be controlled to suit desired outlet steam conditions asdescribed in patent applications Serial Nos. 42,194 and 81,187, filedJune 7, 1960 and January 6, 1961, respectively. 7 FIG. 4 shows theintegrated arrangement of a steamelectric generating plant including thestartup combustion control loading system and the steam generator fluidcontrol system. Outlet steam from steam generator 5 passes throughoutlet steam header 45, through conduit 17 and turbine steam admissionvalve 18 to turbine 19 where the energy of the fluid is converted towork to drive shaft 20 and connecting electric generator 21. Steamexhausts from turbine 19 through conduit 21 to heat sump condenser 10.Cooling water passing through conduit 32 condenses the steam. Thecondensed liquid collects in hotwell 22 and passes through conduit 23 tocondensate pump 24 where the liquid is raised in pressure to the firstworking level. Pump 24 discharges through conduit 25, through heatexchanger 26, conduit 27 to the feedwater pump 28 which raises fluidpressure to the working level of steam generator 5. Pump 28 dischargesthrough conduit 29, feedwater regulator valve 30, through heat exchanger31 to conduit 16 which supplies feedwater to steam generator 5.

Other figure numbers are the same as shown in FIG. 3. Valve 7 controlsfluid pressure in the upstream conduit to a value as preselected inpressure controller 33. Valve 8 is provided with motor operator 34.Valve 9 is provided with power operator 35 which is of the hydraulictype. Valve 12 is provided with pressure controller 36 which regulatesupstream pressure to a preselected value which is the working pressureof the flash tank 6. As

firingrate in burner 160 is increased and surplus heat accumulates inflash tank 6 as a result of flow through valve 7, pressure rises inflash tank 6. The pressure increase opens valve 12 and dumps surplussteam to condenser 10. Valve 15 is provided with pressure controller 37which regulates pressure in the downstream conduit and heat exchanger 31shell. The preselected pressure in 37 regulates the feedwatertemperature passing through conduit 16 to the steam generator inlet.

The flash tank 6 is provided with water level controller 38, whichtransmits a control signal to manual selective switch 39 which permitsthe signal to pass to either valve 13 or valve 14 operators orproportionally to both in a preselected ratio.

In this application the thermocouple 46 shown in FIG. 2 is located in acritical steam admission part of turbine 19, instead of the steam outletheader 45. Either location may be used for the thermocouple. Knownselective means (not shown) may be provided to utilize the highesttemperature of the two locations.

In starting up the steam generator, flow enters the steam generatorthrough conduit 16 and passes through valve 7 to flash tank 6. Valve 9is closed. Heat input from burner raises the temperature and enthalpy ofthe fluid in the steam generator. As steam is liberated at reducedpressure in flash tank 6, it passes through valve 8 to the superheatingsection of the steam generator 5 downstream of valve 9. Flash tank steamis initially used to bring turbine 19 up to speed and may apply somesmall amount of load on the turbine 19. Firing rate has been preselectedin control element 1. The signal from 1 passes through conduit 73 tocontrol element 2, through conduit 78 to the automatic combustioncontrol component 4. The rate of firing preselected in element 1 isexcessive to some moderate degree. The temperature of the steam willbegin to rise. The temperature rise will be detected by thermocouple 46in the turbine metal and control element 3. When the rate of metaltemperature rise exceeds limits established in control element 3,control element 3 through conduit 68 adjusts the signal from element 1as previously described to reduce the signal to element 4, thus reducingfiring rate in burner 100. Air flow in conduit 97 is adjustedparallelly.

Thus firing rate in burner 109 is adjusted to control rate of metaltemperature rise in turbine 19. The same may be made to apply withrespect to rate of metal temperature rise of steam outlet header 45.

As the fiow of steam to the turbine is increased to the limit of flashtank capability, flow is transferred from valve 8 to valve 9. Pressuredownstream of valve 9 is gradually increased to designed working leveland the. startup combustion control loading system is disconnected fromthe automatic combustion control system in element 4 as shown in FIG. 2.

Thus it will be seen that I have provided efficient systems forimproving the operating flexibility of steamelectric generating unitshaving steam generator, turbine generator and auxiliary equipment,including a novel apparatus and system for reducing unit startup timeand costs as Well as to provide the steam generator with capability tovary primary outlet steam temperature to control the rate of metaltemperature rise or fall within the turbine during startup and shutdown,respectively; furthermore, I have provided a novel automatic controlsystem especially for regulating the steam generator automaticcombustion control system during unit startup; also, I have illustratedhow this last mentioned control system may be used in conjunction with asteam generator having a startup fluid bypass control system.

While I have illustrated and described several embodiments of myinvention, it will be understood that these are by way of illustrationonly, and that various changes and modifications may be made within thescope of the following claims.

I claim:

1. In a steam-electric generating plant comprising a steam generatorhaving fluid conducting conduits including a feedwater inlet, asuperheater steam outlet and heat absorption conduits disposedtherebetween, an electric generator, a turbine drive connected to saidelectric generator, said turbine drive having fluid conducting conduits,a heat sump receiving exhaust steam from said turbine drive, fluidconducting conduits serially connecting said superheater steam outletand said turbine drive, a combustion furnace as a source of heat inputto said heat absorption conduits, a supply of fuel and air to saidcombustion furnace, a normal load carrying automatic combustion controlsystem for regulation of said fuel and air supply including fuel and airsupply flow control devices, said fluid conducting conduits being ofmetal and having a critical portion with respect to high temperature,said critical portion being external to the flow path of the products ofcombustion; the invention comprising a startup control system havingmeans for integration with said normal automatic combustion controlsystem and which is responsive to rate of metal temperature change ofsaid critical portion of said fluid conducting conduits, said startupcontrol system comprising means adapted to sense and measure metaltemperature of said critical portion, means adapted to convert saidmeasurement or" temperature to measurement of rate of temperaturechange, means for generating a constant control loading signal forregulating the said fuel and air supply flow control devices, limitingmeans in conjunction with said measurement of rate of temperature changewhich generates a variable output signal as said rate or" temperaturechange increases above a preset value, means for combining said limitingmeans output signal with said constant control signal to reduce fuelflow through said fuel flow control device as said rate of temperaturechange increases above said preset value to maintain said rate of metaltemperature change of said critical portion below a critical value.

2. A startup control system as recited in claim 1 wherein means forgenerating a programmed control loading 7 signal substitutes for saidmeans for generating a constant control loading signal.

3. A startup control system as recited in claim 2 Wherein saidprogrammed control loading signal is programmed with time.

4. A startup control system as recited in claim 3 wherein saidprogrammed control loading signal is programmed with turbine-generatorload.

References Qited by the Examiner UNITED STATES PATENTS 2,962,860 12/60vVintrode et a1. 236-l5 X 3,102,513 9/63 Profos l2240,6

FOREIGN PATENTS 2/59 Great Britain.

1. IN A STEAM-ELECTRIC GENERATING PLANT COMPRISING A STEAM GENERATORHAVING FLUID CONDUCTING CONDUITS IN INCLUDING A FEEDWATER INLET, ASUPERHEAT STEAM OUTLET AND HEAT ABSORPTION CONDUITS DISPOSEDTHEREBETWEEN, AN ELECTRIC GENERATOR, A TURBINE DRIVE CONNECTED TO SAIDELECTRIC GENERATOR, SAID TURBINE DRIVE HAVING FLUID CONDUCTING CONDUITS,A HEAT SUMP RECEIVING EXHAUST STEAM FROM SAID TURBINE DRIVE, FLUIDCONDUCTING CONDUITS SERIALLY CONNECTING SAID SUPERHEATER STREAM OUTLETAND SAID TURBINE DRIVE, A COMBUSTION FURNACE AS A SOURCE OF HEAT INPUTTO SAID HEAT ABSORPTION CONDUITS, A SUPPLY OF FUEL AND AIR TO SAIDCOMBUSTION FURNACE, A NORMAL LOAD CARRYING AUTOMATIC COMBUSTION CONTROLSYSTEM FOR REGULATION OF SAID FUEL AND AIR SUPPLY INCLUDING FUEL AND AIRSUPPLY FLOW CONTROL DEVICES, SAID FLUID CONDUCTING CONDUITS BEING OFMETAL AND HAVING A CRITICAL PORTION WITH RESPECT TO HIGH TEMPERATURE,SAID CRITICAL PORTION BEING EXTERNAL TO THE FLOW PATH OF THE PRODUCTS OFCOMBUSTION; THE INVENTION COMPRISING A STARTUP CONTROL SYSTEM HAVINGMEANS FOR INTEGRATION WITH SAID NORMAL AUTOMATIC COMBUSTION CONTROLSYSTEM AND WHICH IS RESPONSIVE TO RATE OF METAL TEMPERATURE CHANGE OFSAID CRITICAL PORTION OF SAID FLUID CONDUCTING CONDUITS, SAID STARTUPCONTROL SYSTEM COMPRISING MEANS ADAPTED TO SENSE AND MEASURE METALTEMPERATURE OF SAID CRITICAL PORTION, MEANS ADAPTED TO CONVERT SAIDMEASUREMENT OF TEMPERATURE TO MEASUREMENT OF RATE OF TEMPERATURE CHANGE,MEANS FOR GENERATING CONSTANT CONTROL LOADING SIGNAL FOR REGULATING THESAID FUEL AND AIR SUPPLY FLOW CONTROL DEVICES, LIMITING MEANS INCONJUSTION WITH SAID MEASUREMENT OF RATE OF TEMPERATURE CHANGE WHICHGENERATES A VARIABLE OUTPUT SIGNAL AS SAID RATE OF TEMPERATURE CHANGEINCREASES ABOE A PRESET VALUE, MEANS FOR COMBINING SAID LIMIT MEANSOUTPUT SIGNAL WITH SAID CONSTANT CONTROL SIGNAL TO REDUCE FUEL FLOWTHROUGH SAID FUEL FLOW CONTROL DEVICE AS SAID RATE OF TEMPERATURE CHANGEINCREASES ABOVE SAID PRESET VALUE TO MAINTAIN SAID RATE OF METALTEMPERATURE CHANGE OF SAID CRITICAL PORTION BELOW A CRITICAL VALUE.